So, today it has leaked out that Disney will publish a new Gravity Falls Book with the title: Bedtime stories of the strange and unexplained - The Grunkle Stan edition.
This collection of Gravity Falls stories shares Dipper and Mabel’s recollections of the adventures they shared visiting their Grunkle Stan’s Mystery Shack. Each retelling is accompanied by a Grunkle Stan version of the same story written form his gruff, humorous perspective."
The release date is set for: 2/23/2021 ISBN: 9781368064118 With a price of $14.99
It will contain 208 pages and contains of 5-Minute Stories.
Altough the book is a recollection of the series by Dipper and Mabel, it's non-canon to the series.
Gravity Falls Creator Alex Hirsch has shared his suprise on Twitter. He confirmed that he never heard of it and wasn't and isn't involved with this book. He heard about it's excistence just today like anyone else on Twitter. The book is published and written by Disney.
Alex Hirsch has stated on Twitter: Legally Disney can do whatever they want but creatively I would be very disheartened to learn that non-canon books were being written without my participation or consent.